1. Field of the Invention
The present invention relates to a polyimide film and a method of fabricating the same.
2. Description of the Related Art
Matte polymer films usually exhibit diffuse reflection and extinction effect. A matte film usually has a low gloss, a high haze, and soft light reflection. The matte film can offer certain properties such as comfortable tactile feeling and elegant appearance, which can be applied to electronic products, optical lens modules, LCD, advertising banners, packing materials and the like.
Polyimide films have a wide range of applications, one example of which is the flexible circuit board used in the optical lens module of a digital camera. The polyimide film used to make the flexible circuit board of the optical lens module needs to have a substantially dull surface to meet the optical requirement.
In order to reduce the gloss of the polyimide film, some approach may incorporate a delustrant into the polyimide film to increase its surface roughness, so that incident light can be scattered. Conventional delustrants may include inorganic and organic compounds. Examples of inorganic compounds used as delustrant can include silicon oxide, aluminum oxide, calcium carbonate, barium sulphate, and titanium dioxide. However, inorganic compounds may have a relatively high dielectric constant, which may result in poor insulation of the film.
Examples of organic compounds used as delustrant can include polycarbonate (PC), polystyrene (PS), polymethylmethacrylate (PMMA), polyethylene, polypropylene, polyethylene terephthalate (PET), and epoxy resin. However, the organic compound cannot tolerate a temperature above 250° C., which is approximately the temperature at which chemical conversion occurs in the fabrication of the polyimide film. As a result, the use of organic compounds may produce defects in the polyimide film such as cracks or apertures, or form spots of non-uniform color due to uneven melting of the delustrant during the fabrication process.
Therefore, there is a need for a polyimide film with desirable properties of gloss, and address at least the aforementioned issues.